Clickbank is simply a store that let’s people upload products for resale and income. Affiliates sign up in order to promote other peoples products which they choose from a marketplace this allows them to receive a commission in exchange for customers. No many people claim clickbank is a scam however I disagree if you pick the right products and promote them to the right target audience you will see an income in no time at all.
The clickbank marketplace has some very bad products as well as some very very good products which I have personally bought myself.
There are mountains of courses on clickbank however if you do want to make money via this channel it is always better to go directly to the help pages they explain everything in detail.
Dont expect to earn from day one there is a learning curve of about 12 weeks but once you get this right it is relatively easy to make a side income via this method.